ACPICA: Fix deconstification warnings (-Wcast-qual) with acpi_ns_root_initialize().

ACPICA commit 8b3b57c9d11d9c322e09cb06bedac7aa783458fd

Link: https://github.com/acpica/acpica/commit/8b3b57c9


Signed-off-by: Jung-uk Kim <jkim@FreeBSD.org>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>